Regulation of β-Catenin Signaling by the B56 Subunit of Protein Phosphatase 2A

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Science  26 Mar 1999:
Vol. 283, Issue 5410, pp. 2089-2091
DOI: 10.1126/science.283.5410.2089

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Dysregulation of Wnt–β-catenin signaling disrupts axis formation in vertebrate embryos and underlies multiple human malignancies. The adenomatous polyposis coli (APC) protein, axin, and glycogen synthase kinase 3β form a Wnt-regulated signaling complex that mediates the phosphorylation-dependent degradation of β-catenin. A protein phosphatase 2A (PP2A) regulatory subunit, B56, interacted with APC in the yeast two-hybrid system. Expression of B56 reduced the abundance of β-catenin and inhibited transcription of β-catenin target genes in mammalian cells and Xenopusembryo explants. The B56-dependent decrease in β-catenin was blocked by oncogenic mutations in β-catenin or APC, and by proteasome inhibitors. B56 may direct PP2A to dephosphorylate specific components of the APC-dependent signaling complex and thereby inhibit Wnt signaling.

  • * Present address: Departamento de Bioquimica y Biologia Molecular, Universitat de Valencia, Apartado de Correos 73, 46100 Burjassot (Valencia), Spain.

  • To whom correspondence should be addressed. E-mail: david.virshup{at}

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